North Island residents are bracing for a night of wild weather as thunderstorms hit the region.
A spokesman for the Fire Service said they have been dealing with a number of trees that have been downed by strong winds in the Waikato region.
In Auckland a power outage in Albany left 430 households without power overnight.
There were also smaller outages at Wharehine, near Wellsford, that left 50 houses without power and another at East Tamaki where six houses lost electricity.
Residents were warned to secure garden furniture, trampolines and toys; watch out for falling branches; and keep a torch, spare batteries and a phone that works without electricity handy, electricity and gas distributor Vector says.
The company has rostered on extra staff to deal with severe weather.
It's going to get wet as tonight. Don't do dumb stuff on the roads-slow down or just stay home for a rainy dance-off pic.twitter.com/gNf2PKkFbq— Waikato CivilDefence (@CivilDefenceWKT) May 20, 2016
A severe thunderstorm warning was issued for the Auckland region.
The warning also affects people in Waikato, Matamata, Piako, Hamilton and Waipa.
At 9.30pm, the MetService weather radar detected a line of severe thunderstorms lying from offshore Hokianga and down the west coast to Raglan.
The storms, travelling east, are expected to lie from the Kaipara area to Auckland's west coast and across to Hamilton.
These thunderstorms are expected to be accompanied by very heavy rain, large hail and damaging wind gusts.
Very heavy rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous.
Large hail can cause significant damage to crops, orchards, vines, glasshouses and vehicles, and make driving conditions hazardous.
Very strong wind gusts can break branches from trees, damage roofing, and make driving hazardous especially for high-sided vehicles and motorcycles.
MetService earlier put a severe weather watch in place for much of the North Island, with the possibility of heavy thundery rain and severe gale south or south westerlies in Auckland, and North Taranaki.
The watch was then upgraded to a warning in Northland, and a severe thunderstorm warning is in place for Stratford, Ruapehu.
Squally winds and possible tornadoes in the North Island could cause some structural damage, including damage to trees and power lines, and make driving hazardous.
But MetService says if any tornadoes occur, they will only affect very localised areas.
A deep low pressure system is expected to move across the North Island tomorrow, bringing another burst of heavy thundery rain to parts of the North Island.
And tomorrow evening, those southwest gales may become severe in Auckland through to midnight.
Large waves are also likely about the west coast during this time.
Vector has warned people to be aware of possible electrical hazards that could come as a result of the weather.
"Vegetation and debris can blow into lines and can take out power during these kind of weather events," a spokeswoman said.
Really big swells on the west coast this w/end-not safe for boating. If you're keen for a fish, go east coast... pic.twitter.com/LBqpMFr1tV— Waikato CivilDefence (@CivilDefenceWKT) May 19, 2016
She said people should stay clear of fallen power lines and damaged electrical equipment, and treat them as if they are live at all times.
If power is cut, people should switch appliances off at the wall to avoid damage if there is a surge when electricity is restored.
Vector advised the public to keep a torch and spare batteries handy and ensure they had at least one telephone that didn't rely on electricity for operation and to ensure an alternate fuel - like gas for the barbecue - was available for cooking.
Down south, a road snowfall warning has tonight been issued for Arthurs Pass.
MetService said a period of snow is likely near the summit of the road through to near midnight tonight, with 5 to 10cm possibly accumulating on the road until this time.
Really big swells expected on our west coast this w/end-Be extra careful (and maybe avoid rock fishing/singing) pic.twitter.com/aC1ajCCjKy— Waikato CivilDefence (@CivilDefenceWKT) May 19, 2016
MetService meteorologist Hannah Moes said most parts of the country will see rain or showers today; more so in western areas.
"There's a high risk of squally thunderstorms and some severe weather warnings are in place, with heavy rain expected in parts of Fiordland, Westland and Buller."
Kapiti, Wellington and the central North Island may also experience patches of heavy rain, she said.
"The place to be today was Gisborne or Hawke's Bay," Ms Moes said. "They'll remain dry with gusty northwesterlies and warm temperatures in the low to mid 20s."
Tomorrow, the South Island will become fine in the west with showers in the east, continuing through to Sunday.
Central parts of the North Island will become fine on tomorrow, she said.
"The worst of the weather is in the North Island today and tomorrow, then there'll be an improving trend.
"There may just be a few showers at the top and bottom of the North Island on Sunday."
Meanwhile, WeatherWatch is predicting unsettled and stormy weather around the country today.
"The front pushes over the South Island during the morning and afternoon, and then over the North Island during the afternoon and evening.
"It mainly moves in from the west, so as can be expected, western regions of both islands will have rain with heavy falls and thunderstorms, as well as rain squalls at times.
"The east coast of the South Island sees thick high cloud, along with a few spots of rain as the front moves over in the afternoon, then cloud breaking away to some sun - though winds blow strongly from the western quarter.
"The east coast of the North Island sees high cloud thicken from morning, while there's also perhaps a spot of rain in the evening. Otherwise conditions stay mainly dry, while westerlies and northwest winds blow strongly."
Northland Civil Defence says there's potential for harbours - the Hokianga in particular - to be affected by severe weather this weekend.
Homeowners throughout the region are advised to take the usual precautions to secure loose items around their properties, while boaties should check their moorings.
Civil Defence spokeswoman Shona Morgan said a combination of factors - including a large high tide for some areas on the west coast about 10pm tomorrow, could see large waves causing inundation in low-lying foreshore and estuary areas.
"While the worst of the weather's effects are likely to come overnight on Saturday, the large seas are likely to continue for some time," Ms Morgan said.